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Transforming growth factor-beta (TGF-beta)-inducible gene TMEPAI converts TGF-beta from a tumor suppressor to a tumor promoter in breast cancer.


ABSTRACT: TMEPAI is a transforming growth factor-beta (TGF-beta)-induced transmembrane protein that is overexpressed in several cancers. How TMEPAI expression relates to malignancy is unknown. Here, we report high expression of TMEPAI in estrogen receptor/progesterone receptor-negative and human epidermal growth factor receptor-2-negative breast cancer cell lines and primary breast cancers that was further increased by TGF-beta treatment. Basal and TGF-beta-induced expression of TMEPAI were inhibited by the TGF-beta receptor antagonist SB431542 and overexpression of Smad7 or a dominant-negative mutant of Alk-5. TMEPAI knockdown attenuated TGF-beta-induced growth and motility in breast cancer cells, suggesting a role for TMEPAI in growth promotion and invasiveness. Further, TMEPAI knockdown decreased breast tumor mass in a mouse xenograft model in a manner associated with increased expression of phosphatase and tensin homologue (PTEN) and diminished phosphorylation of Akt. Consistent with the effects through the phosphatidylinositol 3-kinase pathway, tumors with TMEPAI knockdown exhibited elevated levels of the cell cycle inhibitor p27kip1 and attenuated levels of DNA replication and expression of hypoxia-inducible fator 1alpha and vascular endothelial growth factor. Together, these results suggest that TMEPAI functions in breast cancer as a molecular switch that converts TGF-beta from a tumor suppressor to a tumor promoter.

SUBMITTER: Singha PK 

PROVIDER: S-EPMC2912953 | biostudies-literature | 2010 Aug

REPOSITORIES: biostudies-literature

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Transforming growth factor-beta (TGF-beta)-inducible gene TMEPAI converts TGF-beta from a tumor suppressor to a tumor promoter in breast cancer.

Singha Prajjal K PK   Yeh I-Tien IT   Venkatachalam Manjeri A MA   Saikumar Pothana P  

Cancer research 20100707 15


TMEPAI is a transforming growth factor-beta (TGF-beta)-induced transmembrane protein that is overexpressed in several cancers. How TMEPAI expression relates to malignancy is unknown. Here, we report high expression of TMEPAI in estrogen receptor/progesterone receptor-negative and human epidermal growth factor receptor-2-negative breast cancer cell lines and primary breast cancers that was further increased by TGF-beta treatment. Basal and TGF-beta-induced expression of TMEPAI were inhibited by t  ...[more]

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